1. Field of the Invention
The present invention relates to a method for the removal of excess amounts of water-soluble amines from Mannich condensation products thereby improving the formulation properties of the Mannich product. More particularly, the present invention relates to removing excess amounts of water-soluble amines from Mannich condensation products to levels below about 0.05xc3x9710xe2x88x923 equivalents of amine per gram of Mannich product (0.05 mEq/g) by filtering the Mannich condensation product with a solid filtering agent having an active surface.
2. Description of the Related Art
Mannich condensation products as fuel and lubricating oil additives are well known in the art and have been widely documented in the patent literature; e.g., U.S. Pat. Nos. 3,368,972; 3,798,247; 4,231,759; 5,399,178; 5,413,614; 5,482,522; and 5,483,523. As fuel additives, Mannich condensation products are particularly effective for the prevention and control of engine deposits, particularly engine intake system deposits, such as intake valve deposits. These additives are based upon the condensation products of a hydroxyaromatic compound, an amine, and an aldehyde.
For example, U.S. Pat. No. 4,231,759 to Udelhofen and Watson discloses reaction products obtained by the Mannich condensation of a high molecular weight alkyl-substituted hydroxyaromatic compound, an amine containing an amino group having at least one active hydrogen atom, and an aldehyde, such as formaldehyde. This patent further teaches that such Mannich condensation products are useful detergent additives in fuels for the control of deposits on carburetor surfaces and intake valves.
The foregoing Mannich condensation products are commonly prepared by the conventional technique of adding the aliphatic aldehyde to a heated mixture of the hydroxyaromatic compound and amine reagents, and then heating the resultant mixture to a temperature between 35xc2x0 to 180xc2x0 C. until dehydration is complete. The reaction may be done in the presence or absence of a solvent. Typical solvents include benzene, toluene, xylene, methanol, and other commercially available aromatic or aliphatic solvents. Light mineral oils and base oils such as those used in blending stocks to prepare lubricating oil formulations in which the product is formed as an oil concentrate are also used. The water byproduct is removed by heating the reaction mixture to a temperature sufficiently high, at least during the last part of the process, to drive off the water. The water may come off alone, or as an azeotrope mixture with the solvent, usually with the aid of vacuum or an inert stripping gas like nitrogen.
U.S. Pat. No. 3,798,247 to Piasek and Karll teaches that the reaction under Mannich condensation conditions, like other chemical reactions, does not go to theoretical completion and some portion of the reactants, generally the amine, remains unreacted or only partially reacted as a coproduct. Unpurified products of Mannich processes also commonly contain small amounts of insoluble particle byproducts of the Mannich condensation reaction that appear to be the high molecular weight condensation product of formaldehyde and polyamines. The amine and amine byproducts lead to haze formation during storage and, in diesel lubricating oil formulations, to rapid buildup of diesel engine piston ring groove carbonaceous deposits and skirt varnish. The insoluble or borderline soluble byproducts are substantially incapable of removal by filtration and severely restrict product filtration rate. These drawbacks were overcome by adding long-chain carboxylic acids to reduce the amount of solids formation from the Mannich reaction by rendering the particulate polyamine-formaldehyde condensation product soluble through formation of amide-type links. In particular, oleic acid worked well at 0.1 to 0.3 mole/mole of alkylphenol. The quantity of unconsumed or partially reacted amine was not mentioned in the patent.
U.S. Pat. No. 4,334,085 to Basalay and Udelhofen discloses that Mannich condensation products can undergo transamination, and this is seen as a solution to the problem of byproduct amine-formaldehyde resin formation encountered by Piasek and Karll in U.S. Pat. No. 3,798,247, above, eliminating the need for using a fatty acid. Basalay and Udelhofen defined transamination as the reaction of a Mannich adduct based on a single-nitrogen amine with a polyamine to exchange the polyamine for the single-nitrogen amine. The examples in this patent suggest that the unconsumed amine and partially reacted amine discussed in U.S. Pat. No. 3,798,247 are not merely unconsumed, but must be in chemical equilibrium with the product of the Mannich condensation reaction. In Example 1 of U.S. Pat. No. 4,334,085, a Mannich condensation product is made from 0.5 moles of polyisobutylphenol, 1.0 mole of diethylamine and 1.1 moles of formaldehyde. To 0.05 moles of this product was added 0.05 moles of tetraethylenepentamine (TEPA) and then the mixture was heated to 155xc2x0 C. while blowing with nitrogen. The TEPA replaced 80 to 95% of the diethylamine in the Mannich product as the nitrogen stripped off the small amount of diethylamine made available by the equilibrium with the Mannich product.
In fuel additive applications, the presence of small amounts of low molecular weight amine in dispersant components such as the Mannich condensation product can lead to formulation incompatibilities (for example, with certain corrosion inhibitors or demulsifiers) and air sensitivity (for example, reaction with carbon dioxide in the air). For example, corrosion inhibitors are typically organic acids. These can react with excess amounts of low molecular weight amines in the Mannich component at room temperature to form insoluble salts and at higher temperatures to form insoluble amides. Incompatibility or air sensitivity is manifested by formation of haze, floc, solids, and or gel in the formulation over time. The incompatibility may occur in the absence of air. Consequently, the manufacturing process for amine dispersant-type fuel additives must include a step to remove low molecular weight amines to low levels. However, in view of the unique chemistry of Mannich condensation products, an effective purification step may not be readily accomplished. In particular, the chemical equilibrium can generate additional low molecular weight amines if the product is heated too much during the purification step. Therefore, there is a need for an economical process to reduce the unconsumed amine and the amine-formaldehyde intermediate to a low level after the Mannich reaction.
There are a number of methods that may be used for removing excess amine after a Mannich condensation reaction. Some possible approaches include washing with water, distillation, and absorption/filtration. However, these techniques must be applied with great care because the chemical equilibrium of the Mannich condensation product has the potential to release more amine during the purification process.
In the area of fuel additives, a typical way of determining the efficiency of the purification step is to measure the low molecular weight amine content of the Mannich product before and after the purification step. The Mannich sample is diluted with solvent and then extracted with water. Analysis of the water extract by gas chromatography or titration yields the amount of water-soluble amine either in weight percent by gas chromatography or milliequivalents of base per gram of Mannich product by titration (mEq/g).
Water washing and simple vacuum distillation are well known techniques for removing water-soluble amines in fuel additive manufacturing processes. Water washing is very complex and relatively costly to implement on a commercial scale. This approach requires multiple washes, and there are recycle streams needed for the solvents that promote phase separation. Fuel additives are good dispersants by nature, and so contacting with water and phase separation become major technical problems.
Simple vacuum distillation is practically limited to amines with normal boiling points well below 200xc2x0 C. For example, U.S. Pat. No. 5,876,468 to Moreton uses a distillation temperature of 80xc2x0 C. for an ethylenediamine-derived Mannich product, but does not give specific temperatures for several other higher boiling amines such as diethylenetriamine or triethylenetetramine. This patent does not disclose any information on water-soluble amine content of the Mannich products in the examples. Also, the Moreton patent does not mention any problem with formulation incompatibilities even though one would expect a problem with some of the higher boiling amines, such as triethylenetetramine, in the formulation used for the diesel engine test in this patent.
The Mannich product made from diethylenetriamine (DETA) presents a typical situation. DETA has a boiling point of about 207xc2x0 C. and is difficult to remove to low levels without water washing. In theory, distillation could be used to remove DETA, but due to its low volatility this requires a very specialized fractionation column with high turnover that operates in tandem with the reactor and results in a solvent byproduct containing DETA and DETA-formaldehyde compounds that must be recycled. This creates another procedure for waste product handling that is often undesirable due to the added complexity and expense in manufacturing the product.
There appears to be no mention in the available Mannich patent literature of the use of solid absorbents combined with filtration to remove low molecular weight amines from Mannich condensation products. However, in the field of polyols, solid absorbents have been used successfully to remove alkaline metal catalyst from the polyols after synthesis.
Thus, the removal of alkaline catalysts from various polyether polyols is also known in the art. For example, U.S. Pat. No. 4,528,364 to Prier discloses a method of removing alkaline catalysts from polyether polyols and polyalkylene carbonate polyols which comprises dissolving the polyol in an aprotic solvent and then contacting the polyol solution with a sufficient amount of an adsorbent to adsorb the alkaline catalysts, followed by physically separating the adsorbent from the polyol solution. This patent teaches that the process described therein is advantageous, as there is no water present to hydrolyze either the polyether polyol or the polyalkylene carbonate polyol. This patent further teaches that preferred adsorbents are aluminum and alkaline earth metal silicates, with magnesium silicate being most preferred. Suitable catalysts taught by this patent include alkali metal borates, alkaline earth metal borates, and ammonium borates.
U.S. Pat. No. 4,507,475 to Straehle et al. discloses a process for purifying crude polyether polyols prepared by anionic polymerization of alkylene oxides in the presence of basic catalysts, wherein the polyols are mixed with water and ortho-phosphoric acid in certain quantity ratios, an adsorption agent is incorporated in the reaction mixture, the mixture is filtered, and the water is removed from the polyol by distillation. This patent teaches that the polyol is mixed with 0.2 to 1.5 parts by weight of water per 100 parts of polyol and that the water content is of decisive importance for the quality of the purification. This patent further teaches that commonly used catalysts are alkali alkoxides and alkali hydroxides, preferably potassium hydroxide. Preferred adsorption agents taught by this patent are natural and synthetic silicas of earth alkali metals or aluminum, preferably synthetic magnesium silicate. This patent also teaches that it is advantageous to use filtration aids such as perlite, kieselguhr and diatomaceous earth, in addition to the adsorption agents.
U.S. Pat. Nos. 5,003,111 and 5,055,496, both to Harper, disclose a process for preparing polyether polyols by polymerizing isobutylene oxide with other alkylene oxides in the presence of an alkali metal catalyst and a crown ether cocatalyst to afford polyols containing low levels of unsaturation. These patents teach that the alkali metal may be derived from any suitable source, including alkali metal hydroxides, alkoxides and phenoxides, and that the alkali metal is preferably potassium or sodium. These patents further teach that the crude polyether polyol is treated to separate the alkali metal and crown ether from the product and that contacting the crude polyol with an adsorption agent, such as magnesium silicate, effectively reduces the alkali metal and crown ether content to acceptable levels. In the examples, these patents teach that the crude polyol was treated with 4% magnesium silicate, 0.5% water, and 1% diatomaceous earth for four hours at 110xc2x0 C. to remove potassium hydroxide and crown ether. The polyol was then filtered through diatomaceous earth, diluted with toluene, water washed, and vacuum stripped to provide the final polyol.
Japanese Kokai (laid-open) Patent Application No. HEI 3-195728 (1991) discloses a process for the purification of polyoxyalkylene polyol which has been synthesized in the presence of alkaline catalyst, which involves neutralizing the crude polyol with mineral acid to a pH of 4.5 to 7.5, followed by adsorption with a synthetic magnesium silicate containing less than 0.5 weight percent sodium, wherein the amount of synthetic magnesium silicate used as adsorbent is 0.05 to 5 weight percent of the polyol. The catalysts used in the polyol synthesis are described as potassium hydroxide, sodium hydroxide, potassium alcoholate, sodium alcoholate, potassium carbonate, sodium carbonate, metallic potassium, and metallic sodium.
Japanese Kokai (laid-open) Patent Application No. HEI 4-197407 (1992) discloses a process for the purification of polyethers, in which catalyst is removed from crude polyethers having a high viscosity, which involves an adsorption treatment performed by the addition of a magnesium silicate adsorbent having an average particle diameter of above 100 micrometers to the crude polyether product, followed by filtration through a filter precoated with a filter aid consisting of diatomaceous earth having an average particle diameter of more than 100 micrometers. Catalysts disclosed for use in the synthesis of the crude polyethers include alkaline catalysts, such as potassium hydroxide and sodium hydroxide, and complex metal cyano compounds, such as zinc hexacyano cobaltate complex and zinc hexacyano iron complex. The complex metal cyano compounds are preferred for making polyether polyols of 8,000 to 50,000 molecular weight.
Japanese Kokai (laid-open) Patent Application No. HEI 9-176073 (1997) discloses a process for manufacturing a propenyl ether compound in which an allyl ether compound is subjected to a rearrangement reaction with the use of an alkali metal hydroxide and/or alkaline earth metal hydroxide as a catalyst, wherein a silicate type adsorbent is used for catalyst removal and purification. This publication teaches that the adsorbent may be selected from acid clay, zeolite, synthetic magnesium silicate, synthetic aluminosilicate, and synthetic magnesium aluminosilicate. This publication further teaches that improved efficiency of catalyst removal can be obtained by the addition of water during the catalyst removal and purification period, wherein the weight ratio of water to silicate adsorbent is from 20:100 to 500:100.
Accordingly, there is a need in the art to have a simple and cost-effective process whereby low molecular weight amines, such as DETA and DETA-formaldehyde intermediates, can be removed from Mannich condensation products. Removing such amines to levels below about 0.05 mEq/g makes the Mannich condensation product compatible with other components used to formulate fuel additive packages, such as organic acids, and eliminates formulation air sensitivity due to carbon dioxide reaction with the low molecular weight amines.
The present invention provides a process which eliminates the problems associated with excess water-soluble amine levels above about 0.05 mEq/g, while avoiding the need for extensive water washing and specialized fractionation columns.
The present invention provides a method for removing excess amounts of water-soluble amines from a diluted crude Mannich condensation product containing about 40 to 80 weight percent crude Mannich condensation product in an inert solvent, which comprises:
a) filtering the diluted crude Mannich condensation product in the presence of about 90 to 230 g of magnesium silicate per equivalent of water-soluble amine in the diluted crude Mannich condensation product and about 20 to 150 g of water per equivalent of water-soluble amine in the diluted crude Mannich condensation product, and in the further presence of about 0.1 to 2%, based on the diluted crude Mannich condensation product, of a filter aid when the particle size distribution of the magnesium silicate is such that the average particle size is below about 50 microns; and
b) recovering a filtrate containing a Mannich condensation product having less than about 0.05 mEq/g of water-soluble amine.
In the present invention the Mannich condensation product is a product of (1) a high molecular weight alkyl-substituted hydroxyaromatic compound wherein the alkyl group has a number average molecular weight of from about 300 to 5,000 (2) an amine which contains an amino group having at least one active hydrogen atom, and (3) an aldehyde, wherein the respective molar ratio of reactants (1), (2) and (3) is 1:0.1-10:0.1-10. Preferred polyalkyl hydroxyaromatic compounds used for the Mannich condensation reaction include polypropyl phenol and polybutyl phenol, especially polyisobutyl phenol.
In the present invention, the crude Mannich condensation product is preferably diluted with inert solvent to give a Mannich condensation product concentration in the range of about 50 to 80 weight percent, more preferably about 60 to 75 weight percent, and most preferably about 65 to 70 weight percent. When utilized, the preferred filter aid employed in the present method is diatomaceous earth.
The magnesium silicate is present at a concentration of about 90 to 230 g per equivalent of water-soluble amine in the diluted crude Mannich condensation product and the filter aid is present at a concentration of about 0 to 2 weight percent, based on the diluted crude Mannich condensation product. The filter aid employed in the present invention is preferably diatomaceous earth.
The water employed in the present invention is present during filtration at a concentration of about 20 to 150 g per equivalent of water-soluble amine in the diluted crude Mannich condensation product. Preferably the water used is deionized water. The filtration is carried out at a temperature in the range of about 40xc2x0 C. to 95xc2x0 C.
Among other factors, the present invention is based on the discovery that excess amounts of water-soluble amines can be effectively removed from Mannich condensation products to levels below about 0.05 mEq/g, preferably below 0.04 mEq/g, by filtering the Mannich condensation product with a solid filtering agent having an active surface. This is particularly surprising since conventional filtration technology can only approach 0.05 mEq/g with the use of large amounts of diatomaceous earth which results in a large amount of valuable product lost in the filter cake and high solid waste disposal costs. In addition, with conventional filtration techniques the filtrate is very hazy because the diatomaceous earth absorbs only a small amount of the water needed to facilitate the adsorption of water-soluble amines. The present purification method also solves a major problem in formulating the Mannich condensation product. Excess amounts of water-soluble amines above 0.05 mEq/g can cause incompatibilities with other components used to formulate fuel additive packages, such as corrosion inhibitors and demulsifiers, and can make the formulation sensitive to air exposure. The incompatibility with other components manifests itself in the formation of insoluble material, haze, flocs, and sediment. Air sensitivity will give similar symptoms.
The present invention involves a method for removing excess amounts of water-soluble amines, primarily low molecular weight amines and their derivatives, from Mannich condensation products. The method of the present invention involves filtration of the Mannich condensation product through a solid filtering agent having an active surface to remove the excess amounts of water-soluble amines. The resulting filtrate contains a Mannich condensation product having less than about 0.05 mEq/g of water-soluble amines, resulting in a product with improved compatibility with other components when used in fuel additive compositions. The present invention will now be described in more detail hereinbelow.
Typically, Mannich reaction products useful in the present invention are obtained by condensing an alkyl-substituted hydroxyaromatic compound whose alkyl-substituent has a number average molecular weight of from about 300 to 5,000, preferably polyalkylphenol whose polyalkyl substituent is derived from 1-mono-olefin polymers having a number average molecular weight of from about 300 to 5,000, more preferably from about 400 to 3,000; an amine containing at least one  greater than NH group, preferably an alkylene polyamine of the formula:
xe2x80x83H2Nxe2x80x94(Axe2x80x94NHxe2x80x94)xH
wherein A is a divalent alkylene radical having about 1 to 10 carbon atoms and x is an integer from about 1 to 10; and an aldehyde, preferably formaldehyde or paraformaldehyde, in the presence of a solvent.
High molecular weight Mannich reaction products useful as additives in fuel additive compositions are preferably prepared according to conventional methods employed for the preparation of Mannich condensation products, using the above-named reactants in the respective molar ratios of high molecular weight alkyl-substituted hydroxyaromatic compound, amine, and aldehyde of approximately 1.0:0.1-10:1-10. A suitable condensation procedure involves adding at a temperature of from about room temperature to 95xc2x0 C., the aldehyde reagent (e.g., formalin) to a mixture of amine and alkyl-substituted hydroxyaromatic compounds alone or in an easily removed organic solvent, such as benzene, xylene, or toluene or in solvent-refined neutral oil, and then heating the reaction mixture at an elevated temperature (about 120xc2x0 to 175xc2x0 C.) while the water of reaction is distilled overhead and separated. The reaction product so obtained is typically finished by conventional filtration and dilution with solvent as desired.
Preferred Mannich reaction products used in the present invention are high molecular weight Mannich condensation products, formed by reacting an alkylphenol, an ethylene polyamine, and a formaldehyde-affording reactant in the respective molar ratios of 1.0:0.5-2.0:1.0-3.0, wherein the alkyl group of the alkylphenol has a number average weight of from about 300 to 5,000.
Representative of the high molecular weight alkyl-substituted hydroxyaromatic compounds are polypropylphenol, polybutylphenol, and other polyalkylphenols, with polyisobutylphenol being the most preferred. Polyalkylphenols may be obtained by the alkylation, in the presence of an alkylating catalyst such as BF3, of phenol with high molecular weight polypropylene, polybutylene and other polyalkylene compounds to give alkyl substituents on the aromatic ring of phenol having a number average molecular weight of from about 300 to 5,000.
The alkyl substituents on the hydroxyaromatic compounds may be derived from high molecular weight polypropylenes, polybutenes, and other polymers of mono-olefins, principally 1-mono-olefins. Also useful are copolymers of mono-olefins with monomers copolymerizable therewith, wherein the copolymer molecule contains at least about 90% by weight of mono-olefin units. Specific examples are copolymers of butenes (1-butene, 2-butene, and isobutylene) with monomers copolymerizable therewith wherein the copolymer molecule contains at least about 90% by weight of propylene and butene units, respectively. Said monomers copolymerizable with propylene or said butenes include monomers containing a small proportion of unreactive polar groups, such as chloro, bromo, keto, ether, or aldehyde, which do not appreciably lower the oil-solubility of the polymer. The comonomers polymerized with propylene or said butenes may be aliphatic and can also contain non-aliphatic groups, e.g., styrene, methylstyrene, p-dimethylstyrene, divinyl benzene, and the like. From the foregoing limitation placed on the monomer copolymerized with propylene or said butenes, it is clear that said polymers and copolymers of propylene and said butenes are substantially aliphatic hydrocarbon polymers. Thus, the resulting alkylated phenols contain substantially alkyl hydrocarbon substituents having a number average molecular weight of from about 300 to 5,000.
In addition to the foregoing high molecular weight hydroxyaromatic compounds, other phenolic compounds which may be used include high molecular weight alkyl-substituted derivatives of resorcinol, hydroquinone, cresol, catechol, xylenol, hydroxy-di-phenyl, benzylphenol, phenethylphenol, naphthol, and tolylnaphthol, among others. Preferred for the preparation of such preferred Mannich condensation products are the polyalkylphenol reactants, e.g., polypropylphenol and polybutylphenol, particularly polyisobutylphenol, whose alkyl group has a number average molecular weight of about 300 to 5,000, preferably about 400 to 3,000, more preferably about 500 to 2,000, and most preferably about 700 to 1,500.
As noted above, the polyalkyl substituent on the polyalkyl hydroxyaromatic compounds employed may be generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have about 2 to 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene, and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene.
The preferred polyisobutenes used to prepare the presently employed polyalkyl hydroxyaromatic compounds are polyisobutenes which comprise at least about 20% of the more reactive methylvinylidene isomer, preferably at least about 50% and more preferably at least about 70% methylvinylidene isomer. Suitable polyisobutenes include those prepared using BF3 catalysts. The preparation of such polyisobutenes in which the methylvinylidene isomer comprises a high percentage of the total composition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808.
Examples of suitable polyisobutenes having a high alkylvinylidene content include Ultravis 10, a polyisobutene having a molecular weight of about 950 and a methylvinylidene content of about 76%, and Ultravis 30, a polyisobutene having a molecular weight of about 1,300 and a methylvinylidene content of about 74%, both available from British Petroleum, and Glissopal 1000, 1300 and 2200, available from BASF.
The preferred configuration of the alkyl-substituted hydroxyaromatic compound is that of a para-substituted mono-alkylphenol. However, any alkylphenol readily reactive in the Mannich condensation reaction may be employed. Accordingly, ortho mono-alkylphenols and dialkylphenols are also suitable for use.
Representative amine reactants are alkylene polyamines, principally polyethylene polyamines. Other representative organic compounds containing at least one  greater than NH group suitable for use in the preparation of the Mannich reaction products are well known and include the mono- and di-amino alkanes and their substituted analogs, e.g., ethylamine, dimethylamine, dimethylaminopropylamine, and diethanolamine; aromatic diamines, e.g., phenylenediamine, diamino naphthalenes; heterocyclic amines, e.g., morpholine, pyrrole, pyrrolidine, imidazole, imidazolidine, and piperidine; melamine, and their substituted analogs.
The alkylene polyamine reactants which are useful include polyamines which are linear, branched, or cyclic; or a mixture of linear, branched, and/or cyclic polyamines wherein each alkylene group contains from about 1 to 10 carbon atoms. A preferred polyamine is a polyamine containing from about 2 to 10 nitrogen atoms per molecule or a mixture of polyamines containing an average of from about 2 to 10 nitrogen atoms per molecule such as ethylenediamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, hexaethylene heptamine, heptaethylene octamine, octaethylene nonamine, nonaethylene decamine, and mixtures of such amines. Corresponding propylene polyamines such as propylene diamine, dipropylene triamine, tripropylene tetramine, tetrapropylene pentamine, and pentapropylene hexamine are also suitable reactants. A particularly preferred polyamine is a polyamine or mixture of polyamines having from about 3 to 7 nitrogen atoms, with diethylene triamine or a combination or mixture of ethylene polyamines whose physical and chemical properties approximate that of diethylene triamine being the most preferred. In selecting an appropriate polyamine, consideration should be given to the compatibility of the resulting Mannich detergent/dispersant with the gasoline fuel mixture with which it is mixed.
Ordinarily the most highly preferred polyamine, diethylenetriamine, will comprise a commercially available mixture having the general overall physical and/or chemical composition approximating that of diethylene triamine but which can contain minor amounts of branched-chain and cyclic species as well as some linear polyethylene polyamines such as triethylene tetramine and tetraethylene pentamine. For best results, such mixtures should contain at least about 50% and preferably at least about 70% by weight of the linear polyethylene polyamines enriched in diethylene triamine.
The alkylene polyamines are usually obtained by the reaction of ammonia and dihalo alkanes, such as dichloro alkanes. Thus, the alkylene polyamines are obtained from the reaction of about 2 to 11 moles of ammonia with about 1 to 10 moles of dichloro alkanes having about 2 to 6 carbon atoms and the chlorines on different carbons.
Representative aldehydes for use in the preparation of the high molecular weight Mannich reaction products include the aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, caproaldehyde, heptaldehyde, and stearaldehyde. Aromatic aldehydes that may be used include benzaldehyde and salicylaldehyde. Illustrative heterocyclic aldehydes for use herein are furfural and thiophene aldehyde, etc. Also useful are formaldehyde-producing reagents such as paraformaldehyde, or aqueous formaldehyde solutions such as formalin. Most preferred is formaldehyde, formalin, or paraformaldehyde.
As discussed previously, the present invention relates to the removal of excess water-soluble amines in the preparation of Mannich condensation products. In a typical procedure for carrying out the present invention, the diluted crude Mannich condensation product is charged to a well-agitated vessel such as a filter-feed tank. With stirring, the vessel is heated to a temperature range of about 40xc2x0 to 95xc2x0 C. The preferred temperature range is about 50xc2x0 to 85xc2x0 C. and more preferably about 60xc2x0 to 75xc2x0 C. The vessel may be kept under a nitrogen pressure of about 0 to 20 psig to minimize water vapor generation. The preferred pressure range is about atmospheric to 5 psig, and the more preferred pressure is atmospheric pressure.
After the desired temperature has been reached, magnesium silicate, such as Magnesol, a synthetic magnesium silicate manufactured by The Dallas Group of America, is thoroughly mixed with the diluted crude Mannich condensation product in the filter-feed vessel.
Typically, about 90 to 230 g of magnesium silicate will be employed per equivalent of water-soluble amine in the diluted crude Mannich product, preferably about 100 to 200 g per equivalent, and more preferably about 110 to 180 g of magnesium silicate per equivalent of water-soluble amine.
When employed, a filter aid in the amount of about 0.1 to 2%, based on the diluted crude Mannich condensation product, is added and thoroughly mixed. The primary purpose of the filter aid is to improve the filtration of the magnesium silicate, although it also has some limited water-soluble amine removal capability. The amount of the filter aid required will depend on the filtration characteristics of the grade of magnesium silicate used. The preferred range of filter aid is about 0.2 to 1.5%, and the most preferred range is about 0.3 to 1%. Typically, the filter aid will be employed when the particle size distribution of the magnesium silicate is such that the average particle size is below about 50 microns. However, the filter aid may also optionally be employed in amounts of about 0.1 to 2%, based on the diluted crude Mannich condensation product, when the particle size distribution of the magnesium silicate is such that the average particle size is equal to or greater than about 50 microns.
In general, the amount of filter aid is optimized for the grade of magnesium silicate used so as to yield an economical filtration rate and minimize product loss in the filter cake. Although the filter aid provides some small benefit for amine removal, it is mainly employed to assure a high enough filtration rate.
Suitable filter aids for use in the present invention include diatomaceous earth (diatomite, kieselguhr, infusorial earth), perlite, asbestos fibers, such as chrysotile, cellulose fibers, such as Solka Floc, carbon-based filter aids, fly ash, and plastics, such as Gellfilt, made from foamed polyurethane. Mixtures of filter aids may also be employed. A preferred filter aid is diatomaceous earth.
The charge order of the magnesium silicate and the filter aid, when employed, is not particularly significant. However, the degree of mixing is an important consideration. The magnesium silicate and filter aid should be mixed to uniformity in the diluted crude Mannich condensation product with no settling in the bottom of the tank.
The diluted crude Mannich condensation product, magnesium silicate, and filter aid are thoroughly mixed for about 0.25 to 2 hours, preferably for about 0.4 to 1.5 hours, and most preferably about 0.5 to 1 hour, at the temperature ranges described above, that is, about 40xc2x0 to 95xc2x0 C., preferably about 50xc2x0 to 85xc2x0 C., and more preferably about 60xc2x0 to 75xc2x0 C.
At this point, water is added to the above mixture. Deionized or distilled water is preferred so as not to introduce excess minerals into the product.
Typically, about 20 to 150 g of water will be employed per equivalent of water-soluble amine to be removed, preferably about 35 to 85 g, and more preferably about 45 to 70 g of water per equivalent of water-soluble amine.
Here, the order of addition is typically an important consideration, particularly when a filter aid is present. The water should be added after the magnesium silicate and filter aid are thoroughly mixed with the diluted crude Mannich condensation product. This will ensure that the wetting of the magnesium silicate and filter aid is uniform, the solids remain mixed in the diluted crude Mannich with no solids settling in the bottom of the vessel, and water loss from evaporation is minimal.
The crude Mannich condensation product, magnesium silicate, filter aid and water are thoroughly mixed for about 0.25 to 3 hours, preferably for about 0.4 to 2 hours, and most preferably about 0.5 to 1 hour, at the temperature ranges described above, that is, about 40xc2x0 to 95xc2x0 C., preferably about 50xc2x0 to 85xc2x0 C., and more preferably about 60xc2x0 to 75xc2x0 C. The temperature must be kept below 100xc2x0 C. to avoid the generation of more water-soluble amine, including amine-formaldehyde intermediates, through chemical equilibrium as these water-soluble amines are being removed.
When utilized, a precoat layer of filter aid is placed onto a pressure filter screen or media to give a thickness of about 2 to 3 mm. However, even when a filter aid is not used with the magnesium silicate, the filter screen may still be precoated with filter aid to facilitate filtration. The diluted crude product is fed to the filter and filtered under pressure up to about 100 psig. Typical final filtration pressures are in the range of about 30 to 60 psig. The filtration is typically carried out at the same temperature as the above mixing of the Mannich condensation product, magnesium silicate, filter aid, and water. The choice of filter aid type as well as the exact water charge can be determined to give a water-soluble amine concentration in the product below about 0.05 mEq/g and an acceptable filtration rate for a manufacturing plant. The filtrate containing the Mannich condensation product having less than about 0.05 mEq/g of water-soluble amine is recovered and then analyzed for water-soluble amine concentration.
When the magnesium silicate particle size distribution is such that the average particle size is greater than about 50 microns, the use of filter aid is not necessary. The crude mixture of diluted Mannich product, magnesium silicate, and water is circulated through the filter and back to the feed tank until a precoat layer of solids is formed on the filter screen. Once there is a precoat layer and the filtrate is clear, the recirculation of filtrate to the feed tank is stopped and the filtered Mannich product having less than about 0.05 mEq/g of water-soluble amine is routed to a finished product tank.